FIX: C2443 Using Structure Member Operand in _asm Block (125799)

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions 1.0
Microsoft Visual C++, 32-bit Editions 2.0
Microsoft Visual C++, 32-bit Editions 2.1
Microsoft Visual C++, 32-bit Editions 4.0
Microsoft Visual C++, 32-bit Editions 4.1
Microsoft Visual C++, 32-bit Enterprise Edition 4.2
Microsoft Visual C++, 32-bit Professional Edition 4.2
Microsoft Visual C++, 32-bit Enterprise Edition 5.0
Microsoft Visual C++, 32-bit Professional Edition 5.0
Microsoft Visual C++ for Windows, 16-bit edition 1.0
Microsoft Visual C++ for Windows, 16-bit edition 1.5
Microsoft Visual C++ for Windows, 16-bit edition 1.52

This article was previously published under Q125799

SYMPTOMS

Under the four conditions described in this article, the following compiler error is generated:

test.cpp(linenumber) : error C2443: operand size conflict

Here linenumber is the assembly instruction in TEST.CPP file that meets the following conditions. This error occurs when the following four conditions are met:

You're using inline assembly.
The size of the source operand on an assembly instruction is different from the size of the destination operand.
The source operand is a member of a structure.
The PTR operator is used to force the operand to the size required.

RESOLUTION

If you are using C++, declare a reference variable initialized with the structure member. Use the reference variable as the source operand in the assembly instruction as shown in this sample code:

Sample Code

/* Compile options needed: /Tp
*/ 

truct Test
{

 int  nInt;
} test1;

void main(void)
{
__asm  mov  bh, BYTE PTR test1.nInt  /* error occurs here */ 

int & nTest = test1.nInt;   /*  these lines work  */ 

__asm  mov  bh, BYTE PTR nTest   /*  these lines work  */ 
}

If you are using C, use a local variable instead of a reference variable.

STATUS

This bug was corrected in Microsoft Visual C++, version 6.0.

Modification Type:	Minor	Last Reviewed:	7/5/2005
Keywords:	kbBug kbfix kbVC600fix KB125799